Rollover control method and system thereof

ABSTRACT

A rollover control method and a system thereof for accurately predicting the occurrence of a rollover and protecting passengers therefrom.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of Korean Application No.10-2002-0084976, filed on Dec. 27, 2002, the disclosure of which isincorporated filly herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a rollover control method and asystem thereof and, more particularly, to a rollover control method anda system thereof adapted to predict a rollover and to prevent a vehiclefrom turning over while the vehicle is in motion and to activate asafety system, thereby protecting the passengers from a rollover.

BACKGROUND OF THE INVENTION

[0003] There is a drawback in the conventional rollover control methodand system in that a model used to predict the rollover is based on asteady state such that an accurate prediction cannot be made in relationto a transient rollover. Further, the conventional rollover controlmethod and system has a wide margin of error, resulting in incorrectresults in predicting a rollover for a moving vehicle.

SUMMARY OF THE INVENTION

[0004] Embodiments of the present invention provide a rollover controlmethod and a system thereof adapted to accurately predict and determinethe possibility of a transient rollover, whereby passengers can beprotected by either preventing the rollover or actuating a safety systemwhen the rollover occurs.

[0005] In accordance with one embodiment of the present invention, thereis provided a rollover control method, the method comprising the stepsof: detecting a steering angle, wheel Revolutions Per Minute (RPM), rollangle, roll rate, yaw rate and vehicle speed detected according to thechange of the operation state of a vehicle; processing the steeringangle and the wheel RPM thus detected by a vehicle dynamical equation,thereby calculating a longitudinal velocity, lateral velocity, yaw rate,roll rate, roll angle, slip angle, and slip ratio; predicting a slipangle transiently generated while the yaw rate, roll rate, roll angle,and vehicle speed thus detected and the valves calculated using thevehicle dynamical equation are processed by a filter; calculating a tirelateral force based on the slip angle thus predicted; performing apre-rollover decision subroutine that estimates the possibility ofgenerating a rollover based on the tire lateral force thus computed;predicting a lateral velocity using the filter when there is apossibility of a rollover at the pre-rollover decision subroutine; andperforming a rollover decision subroutine that assesses the rolloverbased on the lateral velocity thus decided. In a preferred embodimentthe filter is a Kalman filter.

[0006] The pre-rollover decision subroutine comprises the steps of:determining whether a vehicle is turning based on the tire lateralforce; determining whether a vehicle is sharply turning after a firstwarning when it is determined that the vehicle is turning; andperforming a control action in order to prevent a rollover following asecond warning when the vehicle makes a sharp turn.

[0007] The rollover decision subroutine comprises the steps of:comparing the lateral velocity predicted and applied by the filter, witha reference value of a rollover decision; and carrying out a controlaction for a passenger's safety when the rollover is thus predicted.

[0008] In accordance with another object of the present invention, thereis provided a rollover control system, the system comprising: a vehicleoperation state detecting module for detecting a steering angle, a wheelRevolutions Per Minute (RPM), a yaw rate, a roll rate, a roll angle anda vehicle speed that vary in relation to changes in the running state ofthe vehicle; a vehicle dynamics processing module for calculating alongitudinal velocity, lateral velocity, yaw rate, roll rate, rollangle, slip angle and slip ratio by a vehicle dynamical equation that ispreset in a program after receiving the steering angle and the wheel RPMdetected from a vehicle operation state detecting part; an appliedfilter module for predicting the slip angle and the lateral velocity byusing the values calculated from the vehicle dynamics processing moduleand the yaw rate, roll rate, roll angle and vehicle speed detected bythe vehicle operation state detecting module after a predetermined timeperiod; a tire dynamics processing module for calculating a tire lateralforce based on the slip angle value predicted at the applied filtermodule; a pre-rollover decision module for deterring the rollover whenits generation is forecasted based on the lateral force produced fromthe tire dynamics processing module; a rollover decision module forperforming a protective action for the passengers when the overturn isdecided based on the lateral velocity generated from the applied filtermodule after the rollover generation control action is performed by thepre-rollover decision module.

[0009] In a preferred embodiment the applied filter module comprises aKalman filter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For fuller understanding of the nature and objects of theinvention, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

[0011]FIG. 1 is a block schematic diagram of a rollover control systemaccording to an embodiment of the present invention;

[0012]FIG. 2 is a flowchart of a rollover control method according to anembodiment of the present invention;

[0013]FIG. 3 is a flowchart of a pre-rollover decision subroutine inaccordance with an embodiment of the present invention; and

[0014]FIG. 4 is a flowchart of a rollover decision subroutine inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the preferred embodiment of the present inventionwill be described in detail with reference to the accompanying drawings.

[0016]FIG. 1 is a block schematic diagram of a rollover control systemwherein a vehicle operation state detecting system 100 detects asteering angle, wheel RPM, yaw rate, roll rate, roll angle, and vehiclespeed in relation to changes in the running state of a vehicle, andvarious modules for detecting and processing these parameters.

[0017] A rollover control system 200 comprises a vehicle dynamicsprocessing module 210, a filter module 220, a tire dynamics processingmodule 230, a pre-rollover decision module 240, and a rollover decisionmodule 250. In a preferred embodiment, the filter module 220 comprisesan applied Kalman filter. The rollover control system 200 furthercalculates a transient slip angle by receiving the steering angle, thewheel RPM, the yaw rate, the roll rate, the roll angle and the vehiclespeed detected from the vehicle operation state detecting system 100using the filter. The rollover control system 200 then outputs a warningsignal and a rollover control signal by way of performing a rolloverpreliminary decision, and generates a control signal for protecting thepassengers once the rollover is determined.

[0018] An active rear toe-in control system 300 outputs a control signalfor actively controlling the toe-in of the rear side tires according tothe rollover control signal generated from the rollover control system200. A traction control system 400 outputs a control signal for reducingan engine output in order to curtail the engine output of a vehicleaccording to the rollover control signal from the rollover controlsystem 200. A brake control system 500 outputs a brake control signalfor reducing the vehicle speed with respect to the rollover controlsignal from the rollover control system 200.

[0019] An activating system 600 includes an airbag activator 610, aseatbelt pre-tensioner activator 620, a lateral side protectiveactivator 630, a rear toe-in activator 640, an engine activator 650, abrake activator 660, and a warning part 670, wherein control signalsthat are produced from the control system 200, an active rear toe-incontrol system 300, a traction control system 400, a brake controlsystem 500 and the like function to prevent generation of the rollover,thereby generating the rear toe-in control, the engine output reduction,the vehicle speed slow-down and a warning signal. The activating systemfurther causes an airbag to inflate for the passengers' safety during arollover, adjusts a seatbelt pre-tensioner, and activates a lateralprotective apparatus.

[0020] The vehicle operation state detecting system 100 contains asteering angle detecting module 110 for detecting the steering angle, awheel RPM detecting module 120 for detecting a four-wheel RPM, a rollangle detecting module 130 for detecting the roll angle, a roll ratedetecting module 140 for detecting the roll rate, a yaw rate detectingmodule 150 for detecting the yaw rate, and a vehicle speed detectingmodule 160 for detecting the speed of the vehicle.

[0021] The vehicle dynamics processing module 210 of control system 200calculates a longitudinal velocity, a lateral velocity, a yaw rate, aroll rate, a roll angle, a slip angle, and a slip ratio using a vehicledynamical equation that is preliminarily programmed after receiving thesteering angle and the wheel RPM from the steering angle detectingmodule 110 and the wheel RPM detecting module 120 of the vehicleoperation state detecting system 100. The filter module 220 estimatesthe slip angle by receiving the roll angle, the roll rate, the yaw rateand the vehicle speed detected from the roll angle detecting module 130,the roll rate detecting module 140, the yaw rate detecting module 150,and the vehicle speed detecting module 160 of the vehicle operationstate detecting system 100, and by receiving the longitudinal velocity,the lateral velocity, the yaw angle, the roll rate, the roll angle, theslip angle and the slip ratio from the vehicle dynamic processing module210. The tire dynamics processing module 230 computes and decides eachtire lateral force using the predictive slip angle value at the filtermodule 220. The pre-rollover decision module 240 outputs a predeterminedcontrol signal for deterring the predictive rollover after assessing thelateral force from the tire dynamics processing module 230 andpredicting the rollover regarding the turning of the vehicle. Therollover decision module 250 outputs an activating control signal so asto protect the passengers when the rollover is predicted, after judgingthe possibility of the rollover in comparison with the lateralacceleration of a vehicle produced by the filter module 220 byre-inputting the operation state of a vehicle, where the operation statevaries in compliance with the control signal of the pre-rolloverdecision module 240.

[0022] An airbag activator 610 of activating system 600 causes an airbagto inflate according to a control signal from the rollover decisionmodule 250 of the rollover control system 200 for the safety of thepassengers when the vehicle turns over. The seatbelt pre-tensioneractivator 620 adjusts the seatbelt pre-tensioner according to a controlsignal from the rollover decision module 250 of the rollover controlsystem 200 for the passengers' safety during a rollover. The lateralside protective activator 630 prevents the lateral side of the vehiclefrom being crushed inward into the vehicle, according to a controlsignal from the rollover decision module 250 of the rollover controlsystem 200. The rear toe-in activator 640, driven for the toe-in of therear side tires of a vehicle by a control signal from active rear toe-incontrol system 300. Engine activator 650 reduces the engine output basedon a control signal of the traction control system 400. Brake activator660 reduces the vehicle speed via a control system of the brake controlsystem 500. Warning part 670 warns the driver by either emitting a lightsignal or producing a warning sound to inform the possibility of therollover through the warning signal of the rollover control system 200.

[0023] The rollover control system and the method thereof are describedin more detail with reference to FIGS. 2 to 4.

[0024] Once the engine is started in order to move a vehicle, vehicleoperation state detecting system 100 detects the steering angle, wheelRPM, roll angle, roll rate, yaw rate and the vehicle speed that vary inrelation to the change of the operation state of the vehicle (S100). Inaddition, the rollover control system 200 receives the steering angle,the wheel RPM, the roll angle, the roll rate, the yaw rate and thevehicle speed detected from the vehicle operation state detecting system100 to determine the possibility of the rollover.

[0025] In other words, the rollover control system 200 determining therollover of a vehicle is so designed as to input the steering anglevaried in response to a driver's steering operation and the four-wheelRPM to a vehicle dynamics processing module 210 (S110). Further, theroll angle, the roll rate, the yaw rate and the vehicle speed which allchange in relation to the running state of the vehicle are inputted intoan applied filter module 220 (S120).

[0026] The vehicle dynamics processing module 210 computes alongitudinal velocity, a lateral velocity, a yaw rate, a roll rate, aroll angle, a slip angle, and a slip ratio by processing the steeringangle and the wheel RPM detected by a vehicle dynamical equation. Thefilter module 220, meanwhile, predicts and outputs the slip anglegenerated in a transient state by the detected yaw rate, the roll rate,the, roll angle, the vehicle speed and the values calculated by thevehicle dynamical equation preferably via a Kalman filter (S130).

[0027] Moreover, the tire dynamics processing module 230 of the rollovercontrol system 200 receives the predicted slip angle from the filtermodule 220 and outputs the lateral force (Fy) of each tire using a tiredynamical equation (S140). The pre-rollover decision module 240 carriesout a pre-rollover decision subroutine to decide whether a rollover hasoccurred by using each detected tire lateral force (Fy) (S150).

[0028] The pre-rollover decision subroutine compares each tire lateralforce (Fy) that is calculated from the tire dynamics processing module230 whereby when a rollover is predicted to occur, the pre-rolloverdecision subroutine sends a warning signal and control signals, such asa rear toe-in control, a vehicle speed reduction and an engine outputslow-down for preventing the turnover at the same time.

[0029] The filter module 220 receives the roll angle, the roll rate, theyaw rate and the vehicle speed after the operation state of a vehicle ischanged via a control signal. Such a control signal may be the reartoe-in control, the vehicle speed reduction, or the engine outputslow-down, produced from the pre-rollover decision module 240 of therollover control system 200. Filter module 220 then calculates thelateral velocity (Vy). Rollover decision module 250 is applied foraccurately deciding the rollover using the lateral velocity (Vy)calculated to perform a below-mentioned rollover decision subroutine(S170).

[0030] The rollover decision subroutine receives the lateral velocity(Vy) calculated from the filter module 220 at the rollover decisionmodule 250 and compares the lateral velocity with a reference value(CSV: Critical Sliding Velocity) for judging the rollover. When thelateral velocity (Vy) is decided to be larger than the reference valueof the rollover decision, the rollover is preliminarily estimated and anairbag expansion, a lateral side protection of the vehicle, and anadjustment of the seatbelt pre-tensioner are developed in order toprotect the passengers in case of a turnover.

[0031] A vehicle dynamical equation for calculating the longitudinalvelocity, the lateral velocity, the yaw rate, the roll rate, the rollangle, the slip angle, and the slip ratio can be defined by thefollowing mathematical equations 1 through 5. $\begin{matrix}{{{Longitudinal}\quad {Force}},{F_{x}\text{:}}} & \left\lbrack {{Equation}\quad 1} \right\rbrack \\{F_{x} = {m \cdot \left\lbrack {{\overset{.}{V}}_{x} - {r \cdot V_{y}} - {r \cdot p \cdot \frac{m_{s} \cdot h}{m}}} \right\rbrack}} & \quad \\{{{Lateral}\quad {Force}},{F_{y}\text{:}}} & \quad \\{F_{y} = {m \cdot \left\lbrack {{\overset{.}{V}}_{y} + {r \cdot V_{x}} + {\overset{.}{p} \cdot \frac{m_{s} \cdot h}{m}}} \right\rbrack}} & \quad \\{{{Yaw}\quad {Moment}},{T_{z}\text{:}}} & \quad \\{T_{z} = {{I_{z} \cdot \overset{.}{r}} - {I_{xz} \cdot \overset{.}{p}}}} & \quad \\{{{Roll}\quad {Moment}},{T_{x}\text{:}}} & \quad \\{T_{x} = {{I_{x} \cdot \overset{.}{p}} - {I_{xz} \cdot \overset{.}{r}} + {m_{s} \cdot h \cdot \left\lbrack {{\overset{.}{V}}_{y} + {r \cdot V_{x}}} \right\rbrack}}} & \quad\end{matrix}$

[0032] m: total vehicle mass [kg]

[0033] [Equation 1] may be replaced by [Equation 2] $\begin{matrix}{{{Longitudinal}\quad {Velocity}},{V_{x}\text{:}}} & \left\lbrack {{Equation}\quad 2} \right\rbrack \\{{\overset{.}{V}}_{x} = {\frac{F_{x}}{m} + {r \cdot V_{y}} + {r \cdot p \cdot \frac{m_{s} \cdot h}{m}}}} & \quad \\{{{Lateral}\quad {Velocity}},{V_{y}\text{:}}} & \quad \\{{\overset{.}{V}}_{y} = {{{- r} \cdot V_{x}} - {\frac{1}{K_{vy}} \cdot \left\lbrack {{F_{y} \cdot \left( {I_{xz}^{2} - {I_{x} \cdot I_{z}}} \right)} + {m_{s} \cdot h \cdot \left( {{I_{z} \cdot T_{x}} + {I_{xz} \cdot T_{z}}} \right)}} \right\rbrack}}} & \quad \\{{{Yaw}\quad {Rate}},{r\text{:}}} & \quad \\{\overset{.}{r} = {\frac{1}{K_{vy}} \cdot \left\lbrack {{\left( {{m \cdot I_{x}} - {m_{s}^{2} \cdot h^{2}}} \right) \cdot T_{z}} + {m \cdot I_{xz} \cdot T_{x}} - {m_{s} \cdot h \cdot I_{xz} \cdot F_{y}}} \right\rbrack}} & \quad \\{{{Roll}\quad {Rate}},{p\text{:}}} & \quad \\{\overset{.}{p} = {\frac{1}{K_{vy}} \cdot \left\lbrack {{m \cdot \left( {{I_{z} \cdot T_{x}} + {I_{xz} \cdot T_{z}}} \right)} - {m_{s} \cdot h \cdot I_{z} \cdot F_{y}}} \right\rbrack}} & \quad\end{matrix}$

[0034] Roll Angle, φ:

{dot over (φ)}=p

[0035] where,

K _(vy) =m·I _(x) ·I _(z) −m·I _(xz) ² −m _(s) ² ·h ² ·I _(z)

[0036] I_(x): Roll Moment

[0037] I_(z): Yaw Moment

[0038] I_(xz): Multiplication of the Roll Moment and the Yaw Moment

[0039] m_(s): Spring mass

[0040] h: Height between the road and the center of a vehicle$\begin{matrix}{{{Slip}\quad {Angles}},{\alpha:}} & \left\lbrack {{Equation}\quad 3} \right\rbrack \\{{{Slip}\quad {Angle}\quad {of}\quad a\quad {front}\quad {left}\quad {wheel}},{{\overset{.}{\alpha}}_{fl}\text{:}}} & \quad \\{{\overset{.}{\alpha}}_{fl} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{fl\_ ss} - \alpha_{fl}} \right)}} & \quad \\{{{Slip}\quad {Angle}\quad {of}\quad a\quad {front}\quad {right}\quad {wheel}},{{\overset{.}{\alpha}}_{fr}\text{:}}} & \quad \\{{\overset{.}{\alpha}}_{fr} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{fr\_ ss} - \alpha_{fr}} \right)}} & \quad \\{{{Slip}\quad {Angle}\quad {of}\quad a\quad {rear}\quad {left}\quad {wheel}},{{\overset{.}{\alpha}}_{rl}\text{:}}} & \quad \\{{\overset{.}{\alpha}}_{rl} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{rl\_ ss} - \alpha_{rl}} \right)}} & \quad \\{{{Slip}\quad {Angle}\quad {of}\quad a\quad {rear}\quad {right}\quad {wheel}},{{\overset{.}{\alpha}}_{rr}\text{:}}} & \quad \\{{\overset{.}{\alpha}}_{rr} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{rr\_ ss} - \alpha_{rr}} \right)}} & \quad \\{{{Slip}\quad {Ratio}},{s:}} & \quad \\{{{Slip}\quad {Ratio}\quad {of}\quad a\quad {front}\quad {left}\quad {wheel}},{{\overset{.}{s}}_{fl}\text{:}}} & \quad \\{{\overset{.}{s}}_{fl} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{fl\_ ss} - s_{fl}} \right)}} & \quad \\{{{Slip}\quad {Ratio}\quad {of}\quad a\quad {front}\quad {right}\quad {wheel}},{{\overset{.}{s}}_{fr}\text{:}}} & \quad \\{{\overset{.}{s}}_{fr} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{fr\_ ss} - s_{fr}} \right)}} & \quad \\{{{Slip}\quad {Ratio}\quad {of}\quad {rear}\quad {left}\quad {wheel}},{{\overset{.}{s}}_{rl}\text{:}}} & \quad \\{{\overset{.}{s}}_{rl} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{rl\_ ss} - s_{rl}} \right)}} & \quad \\{{{Slip}\quad {Ratio}\quad {of}\quad a\quad {rear}\quad {right}\quad {wheel}},{{\overset{.}{s}}_{rr}\text{:}}} & \quad \\{{\overset{.}{s}}_{rr} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{rr\_ ss} - s_{rr}} \right)}} & \quad\end{matrix}$

[0041] σ_(x) and σ_(x): lateral and longitudinal relaxation length [m]

[0042] The steady state value (α_ss) of slip angle and the steady statevalue (S_ss) of slip ratio can be derived from [Equations 4 and 5]below. $\begin{matrix}{{{Steady}\quad {State}\quad {Values}\quad {of}\quad {Slip}\quad {Angles}},{\alpha_{ss}\text{:}}} & \left\lbrack {{Equation}\quad 4} \right\rbrack \\{{Slip}\quad {Angle}\quad {of}\quad a\quad {front}\quad {left}\quad {wheel}\text{:}\quad \alpha_{fl\_ ss}} & \quad \\{\alpha_{fl\_ ss} = {{- \delta_{fl}} + \frac{V_{y} + {l_{f} \cdot r}}{V_{x}}}} & \quad \\{{Slip}\quad {Angle}\quad {of}\quad a\quad {front}\quad {right}\quad {wheel}\text{:}\quad \alpha_{fr\_ ss}} & \quad \\{\alpha_{fr\_ ss} = {{- \delta_{fr}} + \frac{V_{y} + {l_{f} \cdot r}}{V_{x}}}} & \quad \\{{Slip}\quad {Angle}\quad {of}\quad a\quad {rear}\quad {left}\quad {wheel}\text{:}\quad \alpha_{rl\_ ss}} & \quad \\{\alpha_{rl\_ ss} = {{- \delta_{rl}} + \frac{V_{y} - {l_{r} \cdot r}}{V_{x}}}} & \quad \\{{Slip}\quad {Angle}\quad {of}\quad a\quad {rear}\quad {right}\quad {wheel}\text{:}\quad \alpha_{rr\_ ss}} & \quad \\{\alpha_{rr\_ ss} = {{- \delta_{rr}} + \frac{V_{y} - {l_{r} \cdot r}}{V_{x}}}} & \quad\end{matrix}$

[0043]  where,

δ_(fl)=δ_(fo) +K _(rsf) ·φ−K _(csf) ·F _(yfl)

δ_(fr)=δ_(fo) −K _(rsf) ·φ−K _(csf) ·F _(yfr)

δ_(rl) =K _(rsr) ·φ−K _(csr) ·F _(yrl)

δ_(rr) =−K _(rsr) ·φ−K _(csr) ·F _(yrr)

[0044] δ_(fo): steering angle input valve [rad]

[0045] K_(rsf),K_(rsr): roll steering coefficient of front or rear partof a vehicle [rad/rad]

[0046] K_(csf),K_(csr): cornering stiffness of front or rear part of avehicle [rad/n]

[0047] F_(yfl), F_(yfr),F_(yrl),F_(yrr): lateral force of each tire [N]$\begin{matrix}{{{Steady}\quad {State}\quad {values}\quad {of}\quad {Slip}\quad {Angles}},{S_{ss}\text{:}}} & \left\lbrack {{Equation}\quad 5} \right\rbrack \\{S_{fl\_ ss} = {1 - \frac{V_{x}}{R_{w} \cdot \omega_{fl}}}} & \quad \\{S_{fr\_ ss} = {1 - \frac{V_{x}}{R_{w} \cdot \omega_{fr}}}} & \quad \\{S_{rl\_ ss} = {1 - \frac{V_{x}}{R_{w} \cdot \omega_{rl}}}} & \quad \\{S_{rr\_ ss} = {1 - \frac{V_{x}}{R_{w} \cdot \omega_{rr}}}} & \quad\end{matrix}$

[0048] R_(w): dynamic rolling radius [m], (=0.32)

[0049] ω_(fl), ω_(fr), ω_(rl), ω_(rr): wheel angular velocity inputs[rad/s]

[0050] In addition, tire dynamical equation enumerating the lateralforce of each tire can be defined by [Equations 6 to 8] $\begin{matrix}{{Longitudinal}\quad {Force}\text{:}\quad F_{x}} & \left\lbrack {{Equation}\quad 6} \right\rbrack \\{F_{x} = {F_{xf} + F_{xr}}} & \quad \\{{Lateral}\quad {Force}\text{:}\quad F_{y}} & \quad \\{F_{y} = {F_{yf} + F_{yr}}} & \quad \\{{Yaw}\quad {Moment}\text{:}\quad T_{z}} & \quad \\{T_{z} = {{l_{f}F_{yf}} - {l_{r}F_{yr}} + {\frac{t_{f}}{2}\left\lbrack {F_{xfl} - {F_{yfl}\delta_{fl}} - \left( {F_{xfr} - {F_{yfr}\delta_{fr}}} \right)} \right\rbrack} +}} & \quad \\{\quad {\frac{t_{r}}{2}\left\lbrack {F_{xrl} - {F_{yrl}\delta_{rl}} - \left( {F_{xrr} - {F_{yrr}\delta_{rr}}} \right)} \right\rbrack}} & \quad\end{matrix}$

[0051] Roll Moment: T_(x)

T _(x) =m _(s) ·h·g−(K _(r) ·φ+B _(r) ·p)

[0052] t_(f) and t_(r): front and rear tread [m], (=1.4986/1.5037)

[0053] g: gravitational acceleration (=9.81)

[0054] K_(r): sum of front and rear roll stiffness [N×m/rad]

[0055] B_(r): sum of front and rear roll damping [N×m×s/rad]

[0056] F_(xf),F_(xr),F_(yf),F_(yr) in the [Equation 6] are derived from[Equation 7]

[0057] [Equation 7]

F _(xf) =F _(xfl) +F _(xfr) −F _(yfl)·δ_(fl) −F _(yfr)·δ_(fr)

F _(xr) =F _(xrl) +F _(xrr) −F _(yrl)·δ_(rl) −F _(yrr)·δ_(rr)

F _(yf) =F _(yfl) +F _(yfr) +F _(xfl)·δ_(fl) +F _(xfr)·δ_(fr)

F _(yr) =F _(yrl) +F _(yrr) +F _(xrl)·δ_(rl) +F _(xrr)·δ_(rr)

[0058] Longitudinal Force of each tire (F_(xfl), F_(xfr), F_(xrl),F_(xrr)) of [Equation 7] and lateral force of each tire (F_(yfl),F_(yfr), F_(yrl), F_(yrr)) can be derived from [Equation 8]

[0059] [Equation 8]

[0060] Longitudinal Force of each tire: F_(x)

F _(xfl) =C _(xf) ·S _(fl)

F _(xfr) =C _(xf) ·S _(fr)

F _(xrl) =C _(xr) ·S _(rl)

F _(xrr) =C _(xr) ·S _(rr)

[0061] Lateral Force of each tire: F_(y)

F _(yfl) =−C _(yf)·α_(fl)

F _(yfr) =−C _(yf)·α_(fr)

F _(yrl) =−C _(yr)·α_(rl)

F _(yrr) =−C _(yr)·α_(rr)

[0062] where, C_(xf) and C_(xr): front and rear longitudinal forcestiffness [N]

[0063] C_(yf) and C_(yr) front and rear cornering stiffness [N/rad]

[0064] As illustrated in FIG. 3, when the pre-rollover decisionsubroutine starts, a pre-rollover decision module 240 receives thelateral force (Fy) of each tire from a tire dynamics processing module230 to determine whether any of the tire lateral forces (Fy) becomeszero (S200, S210, S220). In other words, each tire having a zero tirelateral force means that any one of either front or rear outer tire of aturning vehicle is lifted from the road surface, thereby not producingany lateral force (Fy).

[0065] Subsequently, when one of the tires is decided to have a zerolateral force (Fy), the pre-rollover decision module 240 outputs a firstwarning signal to a driver to notify the potential rollover (S230).However, when none of the tires is judged to be zero in lateral force(Fy), the pre-rollover decision module 240 increases in time by dt andperforms the step (S110) that inputs the operation state of a vehicle byreturning to the main routine (S240).

[0066] Furthermore, the pre-rollover decision module 240 determineswhether any of the two tires has a zero lateral force (Fy) following thefirst warning signal (S250). When it is determined that two of theturning tires have a zero lateral force (Fy), the pre-rollover decisionmodule 240 outputs a second warning signal to alarm a possible rollover(S260).

[0067] Moreover, the pre-rollover decision module 240 outputs signalsrequesting for a rear toe-in control, an engine output slow-down, and avehicle speed reduction to an active rear toe-in control system 300, atraction control system 400, and a brake control system 500, as shown inFIG. 1, for preventing a rollover when a vehicle makes a turn on acurved road (S270).

[0068] The active rear toe-in control system 300 outputs a toe-incontrol signal for an inwardly angled adjustment of the rear wheel of avehicle to a rear toe-in activator 640 of an activating system 600.

[0069] The traction control system 400 outputs control signals for athrottle valve opening and a fuel injection to an engine activator 650of the activating system 600 for reducing the engine output.

[0070] The brake control system 500 outputs a brake operation controlsignal reducing the vehicle speed during a turn on a curved road, to abrake activator 660 of the activating system 600.

[0071] The activating system 600 reduces the vehicle speed of a turningvehicle and the engine output, and makes the rear tires toe-in at thesame time in response to the control signal accompanied by the activetoe-in control system 300, a traction control system 400 and a brakecontrol system 500, thereby minimizing the rollover of the vehicle.

[0072] The pre-rollover decision module 240 induces the rolloverpreventive control signal and inputs a roll angle, a roll rate, a yawrate and the change of a vehicle speed into the applied filter module220 by returning to the main routine, executing a step (S160) forcalculating the lateral velocity and determining whether the rollover iscompletely controlled in the turning vehicle (S280).

[0073] Nevertheless, when one of the running vehicle tires is determinedto maintain a zero tire lateral force, the pre-rollover decision module240 signals a warning light to notify the driver that the vehicle is indanger of overturning and extends the time for a predetermined period(dt), and performs a step (S110) for receiving the change of theoperation state of the vehicle so as to assess the rollover with respectto the operation state thereof by returning to the main routine (S290,S295).

[0074] [Rollover Decision Subroutine]

[0075] As illustrated in FIG. 4, once the rollover decision subroutine(S300) is started, a rollover decision module 250 of a rollover controlsystem 200 receives the input of the lateral velocity (Vy) of a turningautomobile generated by a calculation at the filter module 220 andcompares the lateral velocity (Vy) thereof with the first referencevalue for deciding generation of the rollover (S310, S320).

[0076] The first reference value (CSV) is decided by maintaining anAngular Momentum and can be defined as the following mathematicalequation 9. $\begin{matrix}{{CSV} = {{Factor} \cdot \sqrt{\left\lbrack {h^{2} + \left( \frac{t}{2} \right)^{2}} \right\rbrack^{1/2} - h}}} & \left\lbrack {{Equation}\quad 9} \right\rbrack\end{matrix}$

[0077] Factor: tuning value in relation to type of vehicle

[0078] t: tread

[0079] h: height of the central axis of a vehicle from the ground

[0080] Once the lateral velocity (Vy) of a turning vehicle is decided tobe larger than that of the first reference value, the rollover decisionmodule 250 predicts that the turning automobile is about to beoverturned, starting to output control signals for a protection of thepassengers by way of an airbag expansion, a seatbelt pre-tensioneradjustment and a protection of the lateral side of a vehicle from beingdistorted (S340).

[0081] An airbag activator 610 of an activating system 600 ignites anairbag ignition circuit to expand the airbag according to a controlsignal from thee rollover decision module 250 of the rollover controlsystem 200. A seatbelt pre-tensioner activator 620 adjusts the seatbeltfor minimizing the movement of the passengers. A lateral side protectiveactivator 630 prevents a dent in the lateral side of a car caused by acollision.

[0082] Thus, while a vehicle turns on a curved road, the filter module220 precisely estimates the slip angle thereof by inputting the changeof the running state of a vehicle, whereby the rollover can be preventedon the turning vehicle. Even in a case where a vehicle is overturned,injury to the passengers can be minimized by predicting the rolloverbefore the overturn actually happens.

[0083] As apparent from the foregoing, there is an advantage in therollover control method and a system thereof in that the running stateof a vehicle is detected and the lateral force of each tire is predictedin real time, preferably using a Kalman filter, thereby accuratelydetermining whether a transient rollover will occur, and contributing toprevent the rollover, so that the passengers can be protected byactivating a safety system.

What is claimed is:
 1. A rollover control method, the method comprisingthe steps of: detecting a steering angle, a wheel Revolutions Per Minute(RPM), a roll angle, a roll rate, a yaw rate and a vehicle speeddetected according to the change of the operation state of a vehicle;processing said steering angle and said wheel RPM thus detected by avehicle dynamical equation, thereby calculating a longitudinal velocity,a lateral velocity, a yaw rate, a roll rate, a roll angle, a slip angle,and a slip ratio; predicting a slip angle transiently generated whilesaid yaw rate, said roll rate, said roll angle, and said vehicle speedthus detected and the values calculated using said vehicle dynamicalequation are processed by a filter; calculating a tire lateral forcebased on said slip angle thus predicted; performing a pre-rolloverdecision subroutine that estimates the possibility of generating arollover based on said tire lateral force thus computed; predicting alateral velocity using the filter when there is a possibility of ageneration of a rollover at said pre-rollover decision subroutine; andperforming a rollover decision subroutine that assesses the rolloverbased on said lateral velocity thus predicted.
 2. The rollover controlmethod as defined in claim 1, wherein said filter is a Kalman filter. 3.The rollover control method as defined in claim 1, wherein the vehicledynamical equation for calculating said longitudinal velocity, saidlateral velocity, said yaw rate, said roll rate, said roll angle, saidslip angle, and said slip ratio can be defined by the followingmathematical equations: Longitudinal Velocity, V_(x):${\overset{.}{V}}_{x} = {\frac{F_{x}}{m} + {r \cdot V_{y}} + {r \cdot p \cdot \frac{m_{s} \cdot h}{m}}}$

Lateral Velocity, V_(y):${\overset{.}{V}}_{y} = {{{- r} \cdot V_{x}} - {\frac{1}{K_{vy}} \cdot \left\lbrack {{F_{y} \cdot \left( {I_{xz}^{2} - {I_{x} \cdot I_{z}}} \right)} + {m_{s} \cdot h \cdot \left( {{I_{z} \cdot T_{x}} + {I_{xz} \cdot T_{z}}} \right)}} \right\rbrack}}$

Yaw Rate, r:$\overset{.}{r} = {\frac{1}{K_{vy}} \cdot \left\lbrack {{\left( {{m \cdot I_{x}} - {m_{s}^{2} \cdot h^{2}}} \right) \cdot T_{z}} + {m \cdot I_{xz} \cdot T_{x}} - {m_{s} \cdot h \cdot I_{xz} \cdot F_{y}}} \right\rbrack}$

Roll Rate, p:$\overset{\bullet}{p} = {\frac{1}{K_{v\quad y}} \cdot \left\lbrack {{m \cdot \left( {{I_{z} \cdot T_{x}} + {I_{x\quad z} \cdot T_{z}}} \right)} - {m_{s} \cdot h \cdot I_{z} \cdot F_{y}}} \right\rbrack}$

Roll Angle, φ: {dot over (φ)}=p Slip Angles, α: Slip Angle of a frontleft wheel, {dot over (α)}_(fl):${\overset{\bullet}{\alpha}}_{f\quad l} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{f\quad {l\_ ss}} - \alpha_{f\quad l}} \right)}$

Slip Angle of a front right wheel, {dot over (α)}_(fr):${\overset{\bullet}{\alpha}}_{f\quad r} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{fr\_ ss} - \alpha_{f\quad r}} \right)}$

Slip Angle of a rear left wheel, {dot over (α)}_(rl):${\overset{\bullet}{\alpha}}_{r\quad l} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{r\quad {l\_ ss}} - \alpha_{r\quad l}} \right)}$

Slip Angle of a rear right wheel, {dot over (α)}_(rr):${\overset{\bullet}{\alpha}}_{r\quad r} = {\frac{V_{x}}{\sigma_{y}}\left( {\alpha_{rr\_ ss} - \alpha_{r\quad r}} \right)}$

Slip Ratio, s: Slip Ratio of a front left wheel, {dot over (s)}_(fl):${\overset{\bullet}{s}}_{f\quad l} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{f\quad {l\_ ss}} - s_{f\quad l}} \right)}$

Slip Ratio of a front right wheel, {dot over (s)}_(fr):${\overset{\bullet}{s}}_{f\quad r} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{f\quad {r\_ ss}} - s_{f\quad r}} \right)}$

Slip Ratio of a rear left wheel, {dot over (s)}_(rl):${\overset{\bullet}{s}}_{r\quad l} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{r\quad {l\_ ss}} - s_{r\quad l}} \right)}$

Slip Ratio of a rear right wheel, {dot over (s)}_(rr):${\overset{\bullet}{s}}_{rr} = {\frac{V_{x}}{\sigma_{x}}\left( {s_{r\quad {r\_ ss}} - s_{r\quad r}} \right)}$


4. The rollover control method as defined in claim 1, wherein saidpre-rollover decision subroutine comprises the steps of: determiningwhether a vehicle is turning based on said tire lateral force;determining whether a vehicle is sharply turning after a first warningwhen the vehicle is determined to turn as mentioned in the above step;and performing a control action in order to prevent the rollover after asecond warning when the vehicle makes a sharp turn as mentioned in theabove step.
 5. The rollover control method as defined in claim 3,wherein the turning decision of a vehicle is made by a liftingphenomenon of the tire in which the first warning is given when one ofthe tires is decided to be lifted and the second warning is issued whentwo of the tires are judged to be lifted.
 6. The rollover control methodas defined in claim 3, wherein said control action to prevent thegeneration of the rollover comprises a toe-in control for the rear sidetires, an engine output reducing control, and a vehicle speed reducingcontrol.
 7. The rollover control method as defined in claim 1, whereinsaid rollover decision subroutine comprises the steps of: comparing saidlateral velocity predicted and applied by the filter, with a referencevalue of the rollover decision; and carrying out a control operation forpassenger protection when the rollover is predicted in the above step.8. The rollover control method as defined in claim 6, wherein thecontrol operation for protecting the passengers comprises an airbagactivation, a seatbelt pre-tensioner activation and a lateral sideprotection activation.
 9. A rollover control system comprising: avehicle operation state detecting module for detecting a steering angle,a wheel Revolutions Per Minute (RPM), a yaw rate, a roll rate, a rollangle and a vehicle speed angle that vary in relation to changes in therunning state of the vehicle; a vehicle dynamics processing module forcalculating a longitudinal velocity, a lateral velocity, a yaw rate, aroll rate, said roll angle, a slip angle and a slip ratio by a vehicledynamical equation preset in a program after receiving said steeringangle and said wheel RPM detected from said vehicle operation statedetecting module; a filter module for predicting a slip angle and alateral velocity after a predetermined time by using the valuescalculated from said vehicle dynamics processing module and said yawrate, said roll rate, said roll angle and said vehicle speed detected bysaid vehicle operation state detecting part; a tire dynamics processingmodule for calculating a tire lateral force based on said slip anglevalue predicted at said applied filter module; a pre-rollover decisionmodule for deterring the rollover when its generation is predicted basedon said lateral force produced from said tire dynamics processingmodule; and a rollover decision module for performing a protectiveaction for the passengers when the overturn is decided, based on saidlateral velocity generated from said filter module after the rollovergeneration control action is performed by said pre-rollover decisionmodule.